To make the driving experience more pleasurable, there is a continuing effort to enhance the appearance of the interior of the vehicle. Many if not most interior door panels are a three-part composite having a vinyl or cloth skin facing the interior of the vehicle. The skin covers a generally rigid piece of plastic such as a glass-reinforced urethane. For a more premium appearance, typically a padding material will be captured between the vinyl or cloth skin and the more rigid urethane backing. To form the composite panel, the skin will be placed in the lower portion of a mold, the rigid backing will be placed on top of the skin and the foam padding (in a liquid form) will be poured in the mold between the skin and the rigid backing. A chemical reaction of the foam padding material will cure the foam backing, allowing the backing to be "foamed" in place.
Presently the majority of automotive interior door panels in more premium vehicles have a three-dimensional contour which incorporates an arm rest. Therefore, the skin is typically preformed to assume the three-dimensional shape.
In automotive interior trim panels which have a vinyl skin, aesthetic considerations demand the portrait of a leather grain-like appearance. To achieve the grain-like appearance, two methodologies are utilized. In the first technique, a female mold is used to preform the vinyl skin. Therefore, the mold contacts the vinyl skin on a side of the vinyl skin which will be exposed to the vehicle occupant. Therefore, to achieve a grained leather appearance, the mold must be "grained". Graining a mold adds approximately $10,000 to $15,000 to the cost of the mold.
To avoid the cost associated with female molds, a second technique is to use a male mold to preform the vinyl skin. The male mold contacts the vinyl skin on a side of the skin which faces away from the occupant. Therefore, a vinyl skin which has a grained surface prerolled on it from the vinyl skin supplier can be used.
More and more, auto designers seek to have a two-tone effect on interior trim panels. The tones may be distinguished by color and/or texture. One way to achieve the two-tone effect is to simply paint the vinyl skin. Although this seems to be a rather simple solution, it is very difficult since the vinyl skin is a three-dimensional part, and it is virtually impossible to predict where a paint line will end up after the skin has been placed in a mold and the foam backing has been introduced and expanded. Another failure of just painting the skin is that one is limited to differentiations in color only, not in texture of leather grain patterns.
Another technique to provide a two-tone effect is to add an insert to the door panel which is mechanically or adhesively affixed to the door panel over a base vinyl skin. Although the above technique is effective, it requires additional gluing or mechanical fasteners which add to the weight of the vehicle and more importantly to the cost of achieving the two-tone effect.
Another technique to achieve the two-tone effect is to weld two vinyl skins in an overlapping fashion. An example of a sonic welded skin is described in Martin, U.S. Ser. No. 08/161,491filed Dec. 6, 1993, now U.S. Pat. No. 5,418,032. The welded technique of Martin works well; however, in more premium vehicles, an appearance of a dielectric weld line is thought not to be preferable.
Still another method utilizes a closed metal container with internal female grain surfaces in the configuration of the desired panel shape. Powdered vinyl is loaded into the container, and the entire unit is placed in a high output oven set at from approximately 450.degree. F. to 550.degree. F. The mold is then rotated in all directions, and heat imparted to the mold causes the powder to melt and fuse to the internal surface. This creates a continuous skin of a first color to be formed within the container. A portion of the mold is then masked, and a vinyl of a second color is then added into the mold for a similar process as described for the first color. The mold container is then removed from the oven and cooled to room temperature. The mold is then re-opened and the grain skin is extracted for subsequent molding operation. Although the above-noted technique is fairly effective, it still requires a female grain mold and cycle times and the associated capital expenses are high, thereby causing vinyl skins formed by the rotary mold technique to be relatively quite expensive.
To allow for an interior trim panel with a two-tone appearance with a vinyl skin at a far lower cost than what has been previously available, the present invention is brought forth.